Trucks with trailers but no Advertisement

How when I go out, 80% of the trucks with trailers dont have a name or phone number on their truck or trailer? I would think most people would do this since it provides advertisement to everyone on the road. The only thing I can think of is people dont want them knowing where they live. If thats the case why not get a magentic sign or sign on the trailer?Posted via Mobile Device

All of my trucks and trailers don't have anything on them. All trucks and trailers are white and we keep them clean. We have more than enough work to where I've never needed to advertise on my vehicles. I'm very happy with what we have. We still get new people every year from referrals and or neighbors.